He was young, so it's hard to recall exactly how many days that dark stretch lasted. And though his mother doesn't like to keep secrets from her son, Cassandra Mitchell hasn't wanted to talk much about that especially difficult time.

Johnson understands all that, and he knows enough. He knows that at one point, as children, he and his older sister, Ranisha, had nowhere to sleep other than the inside of their mother's car.

That has stayed with the Miami Hurricanes running back to this day.

So, too, has the fact that for much of his life, Johnson has only been able to watch helplessly as Mitchell worked countless overtime shifts as a corrections officer in order to provide for her family.

There were nights she'd work well past midnight to free up time later in her work week so she wouldn't have to miss any of her son's optimist or high school football games.

Now, though, Johnson sees light at the end of the tunnel.

If all goes according to plan, sometime soon, his mother's days will get a whole lot easier. And her struggles, like coping with the season-ending ankle injury that sidelined Johnson last year, will be in the past.

"Everything is for her. Every single thing," Johnson says matter-of-factly. "If I didn't have the childhood I did and it wasn't as tough as it was and my mom didn't struggle the way she did and if I didn't want better for her, I wouldn't play football. … But the reason I play is for her. … It's not for the game. It's not for the attention. It's solely for her, just to get her in a better situation where she doesn't have to work, where she can do what she wants."

But as Johnson prepares for his third season at Miami, the question is, when will that moment come?

The running back says he hasn't given much thought yet to whether this will be his final season at Miami, but there's little question if he stays healthy, his potential NFL future will be a topic of conversation this fall.

On an offense filled with plenty of speed and talent, he was Miami's leading rusher a season ago. Johnson was an electric player capable of breaking free any time he touched the ball on either offense or special teams.

Then on the night the then still-unbeaten, top-10 Hurricanes traveled to Tallahassee, things changed.

Late in the third quarter with Miami down and trying to rally, Johnson charged forward on a fourth-down play. He was tackled short of the first down and his ankle turned awkwardly. Johnson felt not one, but two pops.

Though there was no pain in that moment, he knew instantly the injury was serious.

As he was carted to the locker room, his mind drifted to South Florida where he knew his mother, unable to be attend the game because of health issues of her own, was surely watching and worried.

He tried to reach her as quickly as he could, even trying to crack a joke or two when they finally spoke.

His goal, as it's always been, was to ease her mind.

"It's tougher for her than it is for me," Johnson said. "So I called her right away from the locker room and told her I was fine. Yeah, it's broken, but I'll be alright. … I had to check up on her."

Mitchell can't help but get emotional when she talks about that night, about how her son has always tried to be her protector. But in the days after the injury, it was her down-to-earth, usually-rock solid son who needed support.

Without Johnson, who had already totaled 920 yards and was averaging 6.3 yards-per-carry, the Hurricanes lost three of their final five games. A season that began with so much promise and a seven-game win streak ended in disappointing fashion. One of the worst losses came in Miami's last game, with Johnson watching helplessly as the Hurricanes fizzled in a 36-9 loss to Louisville in the Russell Athletic Bowl.

Miami finished 9-4 and Johnson took it personally, feeling almost guilty for not playing when he felt his teammates needed him the most. Mitchell immediately called on family to help.

"When they lost, he felt like it was his fault," Mitchell said. "He was really down on himself and it was almost as if we were trying to throw him a party to cheer him up. There were hourly cheer-up conversations. For him not to be on the field, I think that hurt him the most."

That pain, along with his mother's encouragement, has driven Johnson through months of intense rehabilitation work. He estimates he's gained about 15 pounds of muscle and he feels his body is ready for the punishment that will surely come as he returns to his role as Miami's featured back.

The Hurricanes' offense will be in transition with a new quarterback under center after Stephen Morris graduated and projected starter Ryan Williams tore his ACL during spring practice. Johnson knows that means more will likely be on his now-broader shoulders. He accepts that challenge.

He's finally let himself start to think about what it will be like to get that first touch when he takes the field for Miami's season opener against the same Louisville team that left the Hurricanes stunned at the end of last season.

He's looking forward to doing his part in avenging that loss and he knows his mother will be there for that moment, and for all that lies ahead — including a decision that could change both their lives.

"Going home and going through this experience, I knew this road, this road to recovery was going to start with her," Johnson said. "I see her work more than she would like to, so I just think about what I'm capable of doing and what I'm able to do if I overcome this injury and don't let it conquer me. I just have to keep fighting and keep playing."